A valid measure actually measures what it says it will measure. To define a measure as valid, one can assess different types of validity. The type of validity of measurement assessed depends on what the researcher wants to know. Criterion validity is one method for assessing the validity of a measure.

In psychometrics, criterion validity is a measure of how well one variable or set of variables predicts an outcome based on information from other variables, and will be achieved if a set of measures from a personality test relate to a behavioral criterion on which psychologists agree.[1] A typical way to achieve this is in relation to the extent to which a score on a personality test can predict future performance or behavior. Another way involves correlating test scores with another established test that also measures the same personality characteristic.[1]

Criterion or concrete validity is the extent to which the measures are demonstrably related to concrete criteria in the "real" world. This type of validity is often divided into "concurrent" and "predictive" subtypes. The term "concurrent validity" is reserved for demonstrations relating a measure to other concrete criteria assessed simultaneously. "Predictive validity" refers to the degree to which any measure can predict future or independent past events.
These variables are often represented as “intermediate” and “ultimate” criteria. For example, let us say we are conducting a study on success in college. If we find out there is a high correlation between student grades in high-school math classes and their success in college (which can be measured by many possible variables), we would say there is high criterion-related validity between the intermediate variable (grades in high-school math classes) and the ultimate variable (success in college). Essentially, the grades students received in high-school math can be used to predict their success in college.